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- Cytochrome P450
This testing can assist with customizing drug therapy by providing metabolic activity information that may explain patient drug responses relevant to CYP2D6 genetic variability. The cytochrome P450 (CYP450) enzymes metabolize many drugs. Individual genetic differences of cytochrome P450 activity can result in the total absence of metabolism to ultrafast metabolism of certain drugs.
This assay does not detect other variants in the CYP2D6 gene that may affect metabolic activity. The metabolism of drugs may also be influenced by race, ethnicity, diet, and other medications. All factors should be considered prior to initiating new therapy. This test result does not rule out the possibility of variant alleles in other drug metabolism pathways.
DNA analysis of the Cytochrome P450 2D6 gene (OMIM 124030) is performed using primer extension chemistry. Multiplex PCR amplifies DNA fragments containing the variants below. Primer extension then generates a biotin-labeled product to permit flow-sorted detection of both normal and variant sequences. Molecular-based testing is highly accurate, but as in any laboratory test, rare diagnostic errors may occur.
*1, *2, *3, *4, *5, *6, *7, *8, *9, *10, *11, *15, *17, *29, *35, *41, and gene duplications.
Variant *5 is a gene deletion. Copy number of duplicated alleles is not determined. Duplications are often functional (whole gene) but may be nonfunctional (partial gene). It is not always possible to determine which allele is duplicated.
*1 represents detection of the normal sequence for the variants tested.
CYP2D6 is involved in the metabolism of opioid analgesics such as codeine, hydrocodone, dihydrocodeine, oxycodone, and tramadol.
Codeine is O-demethylated to its more active form, morphine, by CYP2D6-encoded enzymes. Variation in the CYP2D6 gene can result in ultrarapid, normal (extensive), normal to intermediate, intermediate, and poor metabolizer phenotypes. Ultrarapid metabolizers may experience exaggerated or even potentially dangerous opioid side effects after codeine administration, including euphoria, dizziness, epigastric pain, and/or visual disturbance. For poor metabolizers, a reduced analgesic effect may be observed due to insufficient biotransformation of codeine to its more active form, morphine.
Whole blood or LabCorp buccal swab kit (buccal swab collection kit contains instructions for the use of a buccal swab)
7 mL whole blood or LabCorp buccal swab kit
3 mL whole blood or two buccal swabs
Lavender-top (EDTA) tube, yellow-top (ACD) tube, or LabCorp buccal swab kit (PeopleSoft N° 3177).
Maintain specimen at room temperature or refrigerate at 4°C.
Causes for Rejection
Frozen or hemolyzed specimen; quantity not sufficient for analysis; improper container; wet buccal swab; one buccal swab
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|511380||Opioid CYP2D6 Genotyping||504202||2D6 Genotype:||40425-1|
|511380||Opioid CYP2D6 Genotyping||504203||2D6 Metabolic Activity:||79715-9|
|511380||Opioid CYP2D6 Genotyping||504631||Director Review:||72486-4|
|511380||Opioid CYP2D6 Genotyping||504388||Interpretation:||72880-8|
|511380||Opioid CYP2D6 Genotyping||504389||CYP2D6 Information:||49549-9|